1. Field of the Invention
The present invention relates to an electronic timepiece, and more particularly, to the improvement of layout of a stepping motor and an electronic circuit.
2. Description of the Related Art
There has been known an electronic timepiece arranged such that a stepping motor is driven by a battery as a drive source, the drive of the stepping motor is controlled by an electronic circuit for creating a reference frequency signal based on a clock signal from a quartz oscillator to thereby precisely move hands secured to a wheel train.
In this electronic timepiece, ordinarily, an electronic circuit substrate formed of a synthetic resin film and the like is attached to an end of a coil magnetic core constituting the stepping motor. Since the electronic circuit substrate is larger than the end of the coil magnetic core, it protrudes from the coil magnetic core when viewed in a plane. The protruding portion of the electronic circuit substrate has a punched portion of a pace accelerating/decelerating line pattern connected to a negative conductive section of a power supply and is supported by a main plate and the like. Further, in the stepping motor and the electronic circuit substrate, first, the electronic circuit substrate is bonded to the coil magnetic core, next a coil wire is wound around the coil magnetic core, subsequently the coil wire is connected to an electronic circuit, and finally the assembly of the coil magnetic core and the electronic circuit substrate are assembled to the main plate.
In the stepping motor of the electronic timepiece, the electronic circuit substrate bonded such that it protrudes from the coil magnetic core is supported only by the bonded portion thereof in a cantilever state before it is assembled to the main plate. Therefore, the electronic circuit substrate is unstable in a coil winding process and in a process for assembling it to the main plate. So, a problem arises in that it is difficult to ensure reliable manufacture in that the electronic circuit substrate is liable to be dropped and a bonded surface is liable to be partly detached.
In particular, when an electronic circuit component such as a large IC chip is mounted on the portion of the electronic circuit substrate protruding from the coil magnetic core, a problem arises in that the electronic circuit substrate may be bent and deformed in a coil winding process and in an assembly process and is more liable to become detached from the coil magnetic core, and the portion on which the IC chip is mounted is also liable to become detached.
Further, when the pace accelerating/decelerating unit is cut by a laser beam after assembly of the movement, since the main plate and other components are formed in the linearly traveling direction of the laser beam, something must be provided to prevent these components from being damaged by the laser beam.
Further, when negative conduction provided by a spring member, for example, is positioned on the circuit substrate, stress is applied to a portion different from the bonded portion of the circuit substrate, and thus the bonded portion may become detached.